A field guide to aiding salmon (as preferred by SF and other Tuolumne River diverters)

To no one’s surprise Tuesday, the Turlock Irrigation District board endorsed Tuolumne River fishery improvements that do not involve boosting reservoir releases.

Directors voted 5-0 to support a proposal made by San Francisco in response to a state effort to sharply increase flows for salmon and other native fish on this and nearby rivers.

The city, which gets most of its water from the Tuolumne, calls for projects such as spawning gravel restoation, planting of riverside trees, and control of non-native predators and aquatic weeds.

This approach has long had general support among water suppliers, including TID and the Modesto Irrigation District on the Tuolumne. Tuesday’s vote was for a $34 million plan with specifics on how much habitat would be restored and how the predators could be removed.

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“The district has been and continues to be opposed to increased river flows as the sole solution for a healthy fishery, when nonflow measures are often less costly and more effective,” TID General Manager Casey Hashimoto said.

The proposal is based on extensive studies done on the river by the districts.

The plan from the State Water Resources Control Board involves the Stanislaus, Tuolumne and Merced rivers below their main foothill reservoirs. It calls for 40 percent of pre-dam flows from February through June each year, although they could range from 30 to 50 percent depending on conditions at the time.

The proposal was released last September and drew plenty of debate at five hearing sessions. The state board tentatively plans to release a final plan in October and could vote on it in December.

The 40 percent threshold would roughly double rivers that have been heavily used by farms and cities for more than a century. Environmental and fishing groups seek even higher volume, and they question too much reliance on nonflow measures.

“The lower Tuolumne is now slow-moving and warm, creating ideal habitat for non-native species, such as bass and water hyacinth, that thrive under such conditions,” the Tuolumne River Trust said in a Feb. 2 statement, before the water got unusually high. “Native species, which evolved with faster-moving, colder water, are now at a competitive disadvantage.”

San Francisco supplies about 2.5 million Bay Area residents with water diverted much higher on the Tuolumne than TID and MID. All three share responsibility for lower-river fish.

San Francisco’s proposal for the lower Tuolumne River fishery includes:

▪ Restoration of stream-bed gravel where salmon lay their eggs after returning from a few years in the Pacific Ocean. It would cost $17 million and cover 13 river miles just downstream from La Grange.

▪ Pressure-washing of gravel that has become clogged with sediment, at a cost of $2.4 million.

▪ A $12 million structure, known as a weir, that would block striped bass and other non-native predators near Hughson. The 5-foot-tall weir would have openings for native fish and small boats. It could provide a viewing spot for the public and fish counts for scientists.

▪ Planting native trees such as willow and cottonwood on 12 miles of shoreline. They provide shade, and some river creatures eat the leaves they drop. The cost is $500,000.

▪ Controlling water hyacinth, a nonnative plant that interferes with fish and boats, at a cost of $100,000 in problem years. It got especially bad in the 2012-16 drought but was washed away by this year’s massive flows.